1. Field of the Invention
The invention relates to a method for quality assurance of filtration processes.
2. Description of the Related Art
US 2005/0027484 A1 discloses a method for quality assurance of filtration processes that includes the steps of: inserting a filter element into a filtration device that is selected from among a plurality of filtration devices connected to a shared data network, of which at least some are designed as integrity testing devices in which filter elements are subjected to integrity tests to assess their functional integrity, identifying the inserted filter element, querying integrity information associated with the identified filter element, comparing the queried integrity information with a saved tolerance setting and blocking the selected filtration device if the queried integrity information does not conform to the saved tolerance setting.
The 26th Technical Report published by the Parenteral Drug Association (PDA TR 26, for short) describes in detail the individual steps to be performed in order to assess the integrity of a filter element. In particular, the document describes processes that are to be complied with if a filter element does not pass an integrity test performed on it in a corresponding integrity testing device. For instance, according to PDA TR 26, it is permissible to repeat the integrity test a predefined number of times, in which case the individual integrity tests that are not passed must be documented in order to ensure that a filter element is definitively rejected as unsuitable after failing to pass a predefined maximum number of integrity tests. In practice, PDA TR 26 is implemented on the basis of work instructions given in companies that perform filtration tasks, such as in the biochemical and food industries. Since they are carried out by human staff, however, such work instructions are prone to error and manipulation. This poses significant documentation problems for manufacturers and suppliers when filtration problems occur at a customer's company and it must be clarified whether this is due to defects (for which the manufacturer is responsible) of the filtration system or due to use of filter elements that were improperly tested (by the customer).
DE 101 57 798 B4 discloses a method for performing filtration processes using networked filtration devices. Filter elements inserted into such filtration devices are identified based on machine-readable data carriers (barcode, QR code, transponder, etc.) attached to them, and their identity is communicated to a central filter element database connected to the shared data network. This central filter element database contains filter-element-specific data, in particular, integrity data and product release data, but also specific process and tolerance data. Information can be fed into the filter element database from external sources as well as from the connected filtration devices. Before performing a specific filtration task, the respective filtration device accesses the filter-element-specific data from the filter element database, and is thus able to assess whether the inserted, identified filter element is approved and suitable for the intended purpose. If this is not the case, the filtration device is blocked, at least for the current combination of filter element and filtration task. This process runs automatically and on a software basis, and the corresponding control is executed by means of a process control unit that is also connected to the shared data network. With regard to the known method, it is disadvantageous that the integrity information in the filter element database is not itself subject to any monitoring.
The aforementioned, generic document discloses the practice, before using the filter element, of wirelessly reading the data pertaining to this filter element, which data are saved in a transponder memory attached to the filter element itself. As data pertaining to the filter element, the document lists identification data, limit values for measurement data, measured test values, i.e. a certain type of integrity data, as well as so-called limiting data, such as service life and permitted number of regeneration and sterilization cycles. Such a quality assurance method appears to be more reliable than having human staff execute work instructions. But in complicated borderline cases, such as in the event of unclear integrity test results, the system reveals itself to be too rigid and—depending on the presettings—can result in significant rejection rates or reduced quality assurance.
The invention seeks to solve the problem of providing a more efficient design of the generic quality assurance method, without compromising reliability.